Cobalt carbonyl compounds including dicobalt octacarbonyl, cobalt hydrocarbonyl etc. as such or in modified forms are known for their use as catalysts for a variety of reactions relating to olefinic unsaturated organic compounds including the hydroformylation (oxonation) of olefins, isomerization of olefins, carbonylation of amines and aromatic nitriles, hydrosilation of olefins and the like. These catalyst complexes are subject to serious limitations in that unless carbon monoxide pressures in excess of cobalt carbonyl complex equilibrium values are maintained in their presence, a destructive dissociation into cobalt metal and residue occurs under reaction conditions. Catalytic activity is thus lost and cobalt metal is plated-out on reactor walls and associated transfer piping. From time to time the accumulated metal must be removed by a suitable means, usually by the use of aqueous nitric acid or a similar undesirably corrosive and inconvenient agent.